The present invention relates to transposing apparatus in general, and more particularly to improvements in apparatus for transposing musical compositions or passages in electronic organs, electronic pianos and analogous electronic musical instruments. Still more particularly, the invention relates to improvements in transposing apparatus for the tone generators of electronic musical instruments, especially to improvements in transposing apparatus of the type wherein the main or primary generator is a voltage-regulated high frequency oscillator whose output means is connected with a 12-tone divider circuit having outputs which can furnish the tone frequencies of an octave, and wherein the control voltage for the primary generator is regulated by a switching arrangement having discrete inputs and a common output.
A presently known transposing or transposition apparatus of the above outlined character comprises a switching arrangement having a multi-position switch which can be rotated or shifted to assume any one of twelve different positions each representing a different type of tone. For example, the inputs of this conventional multi-position switch can be connected to the taps of a voltage divider having a single output connected, either directly or through the medium of additional switching means, with the voltage-regulated high frequency oscillator which constitutes the main or primary generator of the transposing apparatus. In accordance with another prior proposal, the inputs of the switching arrangement are connected with the outputs of a 12-tone divider, and the output of the switching arrangement is connected with a phase comparing circuit which controls the main or primary generator. The phase comparing circuit further receives a reference frequency signal.
In each of the aforedescribed conventional transposing apparatus, the movable portion of the multi-position switch must cover different distances (e.g., by rotating about a fixed axis or by performing a translatory movement) in order to place the switch in a desired condition. The distance which the movable part or parts of the switch must cover depends on the nature of the selected transposition, i.e., on the desired change of the musical composition or passage. Such shifting of the movable part of the switch to a different position consumes time and requires at least some attention from the player of the electronic musical instrument. Therefore, the transposing apparatus is normally actuated when the musical instrument is not in actual use. Furthermore, the difficulty of selecting the desired different transposition increases with the speed of making the corresponding adjustment of movable portion of the multi-position switch.